If the people in the study voted for Trump for racist reasons, then the fact that they voted for Obama does not change the fact that they voted for Trump for racist reasons.
Perhaps not, but it certainly gives you something to explain. What was so great about Obama or so terrible about Hillary Clinton that caused him, a black man, to get the votes of racists when she, a white woman, could not? Or did something dramatic shift in society in the past 8 years? If so, what is it? How and why did your country become more racist than it was? And you can't really say "A black man was elected and it woke racists up" because Obama was elected not once, but twice.
Maybe it is the identity politics push we've been seeing, and maybe that made some white people decide to identify as white and act and vote according to what they have come to see as "white interests". Is that what you are saying? If so, then what I have been saying about identity politics in past threads is consistent with that. White racism is the biggest identity politic after all.
And if racism is why Trump won, what do you suggest for winning against him next time around? Less demonization of white men and empathetic conversation? Or further baiting of a race war? The article (Vox article no less) states that the best way to undo racism is to create empathy within the racists with non-confrontational conversation building upon common experience. I've been saying that for a long time here too. The best way to curb bigotry or prejudice is to go at the root of it in a way everybody can relate to. Everybody has at some time in their life been attacked or ostracized for a personal trait beyond their control. If not on race, then on something else, be it gender, sexual orientation, height, weight, physical attractiveness, intelligence, being a ginger (lol), religion, etc. Empathy can be created through that.